内存屏障生成器
阅读 Joseph Albahari 的线程教程，提到以下内容作为内存屏障的生成器：
- C# 的
lock语句 (Monitor.Enter/Monitor.Exit) Interlocked类上的所有方法- 使用异步回调线程池 - 其中包括异步委托、APM 回调和任务延续
- 设置和等待信令构造
- 任何依赖于信令的内容，例如启动或等待任务
此外，Hans Passant 和 Brian Gideon 添加了以下内容（假设其中没有一个适合其中之一）前面的类别）：
- 启动或唤醒线程上下文
- 切换
Thread.Sleep()
我想知道这个列表是否完整（如果实际上可以制作完整的列表）
编辑
- 易失性（读取意味着获取栅栏，写入意味着释放栅栏）
Reading Joseph Albahari's threading tutorial, the following are mentioned as generators of memory barriers:
- C#'s
lockstatement (Monitor.Enter/Monitor.Exit) - All methods on the
Interlockedclass - Asynchronous callbacks that use the thread pool — these include asynchronous delegates, APM callbacks, and Task continuations
- Setting and waiting on a signaling construct
- Anything that relies on signaling, such as starting or waiting on a Task
In addition, Hans Passant and Brian Gideon added the following (assuming none of which already fits into one of the previous categories):
- Starting or waking up a thread
- Context switch
Thread.Sleep()
I was wondering if this list was complete (if a complete list could even be practically made)
EDIT additions suggested:
- Volatile (reading implies an acquire fence, writing implies a release fence)
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这是我对这个主题的看法，并试图在一个答案中提供一个准完整的列表。如果我遇到其他人，我会不时编辑我的答案。
人们普遍认为会导致隐式屏障的机制：
Monitor类方法，包括 C# 关键字lockInterlocked类方法。Volatile类方法 (.NET 4.5+)。SpinLock方法包括Enter和Exit。Thread.JoinThread.VolatileRead和Thread.VolatileWriteThread.MemoryBarrier易失性关键词。BeginInvoke方法等。ManualResetEvent、AutoResetEvent、CountdownEvent、Semaphore、Barrier等。Control.Invoke、Dispatcher.Invoke、等封送操作SynchronizationContext.Post等。推测（但不确定）导致隐式障碍的机制：
Thread.Sleep（由我自己和可能其他人提出，因为代码表现出内存屏障问题可以用此方法修复）Thread.YieldThread.SpinWaitLazy取决于哪个LazyThreadSafetyMode指定了其他值得注意的提及：
lock或Interlocked.CompareExchange。1 这解释了为什么
BackgroundWorker可以在CancellationPending属性的基础字段上没有易失性的情况下正常工作。Here is my take on the subject and to attempt to provide a quasi-complete list in one answer. If I run across any others I will edit my answer from time to time.
Mechanisms that are generally agreed upon to cause implicit barriers:
Monitorclass methods including the C# keywordlockInterlockedclass methods.Volatileclass methods (.NET 4.5+).SpinLockmethods includingEnterandExit.Thread.JoinThread.VolatileReadandThread.VolatileWriteThread.MemoryBarriervolatilekeyword.QueueUserWorkItem,Task.Factory.StartNew,Thread.Start, compiler suppliedBeginInvokemethods, etc.ManualResetEvent,AutoResetEvent,CountdownEvent,Semaphore,Barrier, etc.Control.Invoke,Dispatcher.Invoke,SynchronizationContext.Post, etc.Mechanisms that are speculated (but not known for certain) to cause implicit barriers:
Thread.Sleep(proposed by myself and possibly others due to the fact that code which exhibits a memory barrier problem can be fixed with this method)Thread.YieldThread.SpinWaitLazy<T>depending on whichLazyThreadSafetyModeis specifiedOther notable mentions:
lockorInterlocked.CompareExchange.MarshalByRefObjectseems to suppress certain optimizations in subclasses which may make it appear as if an implicit memory barrier were present. Thanks to Hans Passant for discovering this and bringing it to my attention.11This explains why
BackgroundWorkerworks correctly without havingvolatileon the underlying field for theCancellationPendingproperty.我似乎记得 Thread.VolatileRead 和 Thread.VolatileWrite 方法的实现实际上会导致完整的栅栏，而不是半栅栏。
这是非常不幸的，因为人们可能会在不知不觉中依赖这种行为；他们可能编写了一个需要完整栅栏的程序，认为他们需要半栅栏，认为他们得到了半栅栏，并且如果这些方法的实现确实提供了半栅栏，将会感到非常惊讶。
我会避免这些方法。当然，我会避免所有涉及低锁代码的事情，除了最琐碎的情况之外，我不够聪明，无法正确编写代码。
I seem to recall that the implementations of the Thread.VolatileRead and Thread.VolatileWrite methods actually cause full fences, not half fences.
This is deeply unfortunate, as people might have come to rely upon this behaviour unknowingly; they might have written a program that requires a full fence, think they need a half fence, think they are getting a half fence, and will be in for a nasty surprise if an implementation of these methods ever does provide a half fence.
I would avoid these methods. Of course, I would avoid everything involving low-lock code, not being smart enough to write it correctly in anything but the most trivial cases.
volatile关键字也充当内存屏障。请参阅 http://blogs.msdn.com/b/布拉达/archive/2004/05/12/130935.aspxThe
volatilekeyword acts as a memory barrier too. See http://blogs.msdn.com/b/brada/archive/2004/05/12/130935.aspx